c# datagridview selectionchanged事件错误

本文关键字：错误 事件 selectionchanged datagridview | 更新日期: 2023-09-27 18:12:11

当我在datagridview中使用selectionchanged事件时。如果我点击列标头它会给我这个异常NullReferenceException未被用户代码处理对象引用未设置为对象的实例。

这是我的代码

    private void dgvEvents_SelectionChanged(object sender, EventArgs e)
    {
        //
        //Select By EventID Operation.
        //
        eventID = int.Parse(dgvEvents.Rows[dgvEvents.CurrentRow.Index].Cells["EventID"].Value.ToString());
        EventEntity = EventsMethods.SelectByID(eventID);
        txtEventName.Text = EventEntity.Name;
        cboxEventsCategories.SelectedValue = EventEntity.EventCategoryID;
        dateTimePickerEvent.Text = EventEntity.Date.ToString();
        txtBenefNum.Text = EventEntity.BeneficiariesNumber.ToString();
        txtResultB.Text = EventEntity.ResultBefore.ToString();
        txtResultA.Text = EventEntity.ResultAfter.ToString();
        txtPercentage.Text = EventEntity.Percentage.ToString();
        //
        //Show EventsMembers.
        //
        FillEventsMembersDGV();
    }

c# datagridview selectionchanged事件错误

其中一个是返回一个空对象…

dgvEvents.Rows[dgvEvents.CurrentRow.Index].Cells["EventID"].Value.ToSt‌​ring()

可以是下列任意一个:

dgvEvents
dgvEvents.CurrentRow
dgvEvents.Rows[....]
dgvEvents.Rows[....].Cells
dgvEvents.Rows[....].Cells["EventID"]
dgvEvents.Rows[....].Cells["EventID"].Value
最好的方法是把它分成几个步骤: 
    var curRow= dvgEvents.CurrentRow;
    if ( curRow != null )
         var index = curRow.Index;
// etc

你很可能会得到这个错误，因为它触发事件时，它不是一个有效的选择(即。-1)因此抛出这个异常。试试这个:

   if ((e.RowIndex >= 0) && (e.ColumnIndex >= 0))
    {
            //
            //Select By EventID Operation.
            //
            //Also, use Convert.ToString() rather than .ToString();
            eventID = int.Parse(Convert.ToString(dgvEvents.Rows[dgvEvents.CurrentRow.Index].Cells["EventID"].Value));
            EventEntity = EventsMethods.SelectByID(eventID);
            txtEventName.Text = EventEntity.Name;
            cboxEventsCategories.SelectedValue = EventEntity.EventCategoryID;
            dateTimePickerEvent.Text = EventEntity.Date.ToString();
            txtBenefNum.Text = EventEntity.BeneficiariesNumber.ToString();
            txtResultB.Text = EventEntity.ResultBefore.ToString();
            txtResultA.Text = EventEntity.ResultAfter.ToString();
            txtPercentage.Text = EventEntity.Percentage.ToString();
            //
            //Show EventsMembers.
            //
            FillEventsMembersDGV();
    }
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